1. Field of the Invention
The invention relates to a mechanical crayon pen, and particularly to a mechanical crayon that has an internal cartridge to hold multiple crayon sticks inside so a particular colored crayon can be conveniently and quickly installed in the crayon pen.
2. Description of Related Art
With reference to FIG. 7, a conventional mechanical crayon pen has a barrel (50) and multiple sectional sleeves (52). The barrel (50) has a bottom outlet (not numbered) and a top inlet (not numbered). The multiple sectional sleeves (52) are slidably stacked inside the barrel (50). Each sleeve (52) has a short crayon stick (51) mounted in and protruding from the sleeve (52). Only the sleeve (52) and crayon stick (51) at the bottom outlet of the barrel (50) be seen and used to draw.
The crayon stick (51) is changed by pulling the sectional sleeve (52) at the bottom outlet out of the barrel (50) and pressing it into the top inlet until a desired crayon stick (51) appears at the bottom outlet. The conventional mechanical crayon pen has the following drawbacks:                1. The sectional sleeves (52) with the short crayon sticks (51) are not sold individually. When one of the crayon sticks (51) is used up or one of the sectional sleeves (52) is lost, a complete set of new sectional sleeves (52) with the short crayon sticks (51) must be bought to complete the selection of colors in the conventional mechanical crayon pen. The unused sectional sleeves (52) with the short crayon sticks (51) are a waste for the user.        2. Because the sectional sleeves (52) are stacked inside the barrel (50) in sequence and a specific crayon stick (51) cannot be selected directly, individual sectional sleeves (52) must be removed from and replaced in the barrel (50) one by one until the desired crayon stick (51) appears. Therefore, exposing the desired color stick (51) is troublesome.        
Another conventional mechanical crayon pen incorporates features of a mechanical pencil and multiple crayon sticks to change the crayon sticks easily. However, the crayon sticks are stored in a separate case. Hence, the user has to carry the mechanical crayon pen with the separate case of crayon sticks to be able to draw with different colors.
The present invention has arisen to provide a mechanical crayon pen to obviate the foregoing drawbacks of conventional mechanical crayon pens.